Smoke tracer composition



2,823,105 .SMOKE TRACER COMPOSITION =Thomas Stevenson, Huntingdon Valley, and WinstonW. Cavell, lfhiladelphia, Pa., assignors to the'United States .ofAmenca as represented by the Secretary of the Army No Drawing. Application January 27, 1955 Serial N0.-484',599

V 5 Claims. .(Cl..52 24) (Granted underTitle35, UJS. Co'de (1952), sec.""266) Ihe=invention described hereinamay be'm'anufactured and .used by or for the Government forggovernmental purposes without -the payment to us of any royalty thereon.

.Oursinvention relates to compositions for smoke traclingiproje'ctile trajectory.

i In-thepatent-to -Stevenson et al., No. 2,115,047, dated *April 26,1938, it -was -taught,--in respect'of the use of arms -on theiground, that tracing of initial trajectory was adisadvantageto gunnery. The inventionof that patent presented a solution in the form of igniter compositions Whose combustion left'no trace. According'to thequantity and rate of burning of theStevenson igniter compositon which effected ignition of an underlying flametracer composition, a delay was obtained whereby no visible trace was produced until a selected'distance had been covered.

From the extensive aerial gunnery experiences of World War II, stemming from air combat operations therefore unparalleled in scope, it I developed that the accuracy of pilot-gunners was greatly enhanced when projectiles emanating ffromthe. guns 'of .their aircraft, particularly wing-mounted (guns, produced a smoke trace-or trail which in its visual'elfect was connected to .the aircraft. Air combatpersonnel had resorted to various field expedients,.such as a coating of ammunition with oils and waxes ofvarious types, to cause the ammunition, when fired, to "leavea more or less satisfactorysmokeltrace from the very muzzle of the weapon.

The elfect of ,conventionaLiflame tracers .stems;from what is actuallyapointlikeisource of light that is ineffectual untilayprojectile so tracedis far enoughfforward of an aircraft'to render the base or tr'ac'erend of the projectile visible to the gunner. Thereafter a'line trace eifect results but it is disconnected from the aircraft and'fails toyield the accuracy of aim attainable with a trace whose origin is at themuzzle of'theaircrafts gun. 'Also,-.in night firing, conventional flame tracercomposi- "tion adversely afifects the dark adaptation of the human eye and reveals or emphasizesposition' to the enemy.

Accordingly,theprincipal object of our invention is the provision of ,improved projectile trajectory smoke tracer compositions that are susceptible of direct ignitionby propellant and, in such small quantity as can be accommodatedin the space.provided in projectiles for tracer, operative to produce smoke trail originating at gun ,muzzle and extending inadequate density over at least 1,000 yards of trajectory, without emission oflig'ht or with .emission of a controlled" intensity.

:A further object of our invention .is to1provideimproved'formulations'of'the kind described for the production of smoke trail in various colors.

At the time'of undertaking of the developments leading to our invention, we were aware thatimany types of smoke producing compositions had been taughffor' various other purposes. ..In aneifort'to Jadapt'such; prior art compositionsto our.objects,man'y Weretesteli with unsuccessful results. 'Our surveyo'f the-priorart reflected thatsmoke compositions were comprised of sublimable dyestuffs and other sublimable and readily vaporizable materials to- .gether with oxidizing agents such as: chlorates, perchlorates, dichromates, dioxides, nitrates, black powder, nitro- :guanidine, nitrosoguanidine; pyrophoric metals; and such .fuels as sucrose, lactose, pitch, sawdust, carbon, hexa- 'chloroethane and other carbonaceous materials. Additionally, waxes, minerals, clays, earths,'powdered glass, varnishes and inorganic compounds were foun'd'to be utilized in compositions as binders, cooling agents, abrasives and burningrate regulators.

It is pertinent to the advantages inherent in "the compositions of our invention, as'will be 'detailed'later,l'to

observe thatthe prior art compositions are packaged and utilized in pots, canisters, "fuze trains and ignited by separate igniter compositions that are initiated mechanically as by removal of a cover or actuation of a draw stringor'b'y impact. The prior art compositions also are packed under relatively low pressure and their "usual application is to'the production of'voluminous smoke, or smoke and flame signals for longer periods, running intohours, involving quantities of the order of one to four pounds of composition per canister.

As will be shown, prior art smoke compositions have been governed 'by considerations notably diiferent'from those that rule in the case of smoke tracercompositions forprojectiles.

The requirementth'at the smoke trail originate 'atithe muzzle of the gun makes necessary a composition ignitible directly by the projectile propellant within an element 'oftime less thanprojec'tile time in the'gun barrel. This is of the order of less than one hundredth of "a second andhence precludes an intermediaryigniting means. In this regard, chlorate, perchlorate, .dichromate, nitrate, black powder,nitroguanidine and other conventional: types of smoke compositions were tested and found unreliable in function or to leavecorrosive residue in the gun'barrel. Space limitations in projectiles ordinarily impose a total composition quantity within a range of '5-80 grains in-the face of a requirement that smoke trail must'be'of visible density over adistan'ce of at least 1000 yards. This is in contrast with'p'rior art smoke compositionsthat are used in comparatively large quantities as previously observed. Projectile smoke tracer 'compositionsalso must be susceptible of undergoing high compression of the order of 110,000 p. s. i. during'loadin'g without igniting. Such composition after being compressed under 110,000 p. s. i. shows a density of -2 grams per'cubic-centimeter. Loading pressures of that order are required to prevent dislodgement of'the' composition by forces atplay-duringprojectile' launching. By comparisomprior art smoke compositions are not subject to high accelerational vforces 'while open-end packaged as is the case with our compositions and hence need not be consolidated at such high pressures. Stability in storage in exposure to the acidic products of decomposition of propellant to which our smoke tracer composition necessarily must be exposeddirectly also is a requirement peculiar, distinguishing from the prior art compositions. Still another requirement is that the smoke tracer composition shall not leave a corrosive residue-in the gun barrel as results When'oxidizers such as chlorates and perchlorates are used.

In searching for a formulation that would perform reliably and satisfactorily under conditions imposed in projectile trajectory smoke tracing, we discovered that a composition comprising as-basic ingredients an "alkaline earth-peroxide, :a combustible resin and isublimable material would yield the required performance. More specifically, our formulation comprises an alkaline peroxide "such as strontium or barium peroxide as :a'n oxidizer in a proportion ranging from 50% to a stability upon having been conventionally loaded into projectile ammunition. In test firing, a heavy, White smoke trail behind the bullet for approximately 1000 yards resulted. The same results were attained with a formulation wherein anthracene was substituted for ortho dihydroxy benzene known in the trade as pyrocatechol, with the exception that the smoke trail or trace was then black. In relying upon the ranges of proportion of ingredients forming a part of our discovery, excellent results are attained in formulation with a variety from amongthe classes of materials recited as basic ingredients. For example, our research and firing tests have demonstrated that barium, calcium, lithium and lead peroxides may be utilized in lieu of strontium peroxide. Also a commercial grade of rosin or Amberlite resin may be used in place of calcium resinate. And we have determined that in accordance with our formulation the sublimable material may be selected freely according to the color that it is desired to impart to the smoke trace. We prepared and tested many compositions containing various sublimable compounds as the sublimable material ingredient, singly and in combinations. These included many dyes of dilferent color, subliming temperature and vaporizing characteristics. Our tests included loading and firing in various projectiles representative in design and caliber of the gamut of arms. We obtained smoke trails of various color, density and length and the information upon which our proportion of ingredients is based. As a sublimable material, dyes of the anthraquinone series are preferred for the reason that they participate to give the most consistently satisfactory compositions with regard to the several requirements governing projectile trajectory smoke tracer.

We discovered that our formulations could be modified by including a fourth ingredient in quantity operative to produce dual purpose tracer compositions that in the daytime yield only a smoke trail without discernible light but emit glow that is readily resolved in the dark with the unaided eye to a distance in excess of one thousand yards. We have accomplished this result by addition of an experimentally established quantity of a pyrophoric metal in the usual powdered form.

Notable advantages deriving from our improved projectile trajectory tracer compositions are: direct ignitibility; trail of marked persistence enabling a gunner to observe his fire as an extension of his aircraft into space; stability in storage; noncorrosive residue in gun barrel; color trails for code purposes and for range estimation by loading appropriate quantities of composition yielding different colors at successive stages of a trajectory; unimpaired night time visual acuity or at least materially less affected than by conventional flame tracer.

Examples of our preferred compositions are as follows:

. Percent Ingredient: by weight Strontium peroxide 70 Calcium resinate 15 l-methylaminoanthraquinone 15 This formulation yields a red smoke trace visible by daylight to one thousand yards with no effect visible in the dark.

Percent Ingredient: by weight Strontium peroxide 70 Calcium resinate l0 l-methylaminoanthraquinone l5 Powdered magnesium 5 This formulation yields a red smoke trace visible by daylight to one thousand yards with a glow resolvable in the dark to one thousand yards.

This formulation yields a red smoke trace visible by daylight to one thousand yards with no effect visible in the dark and is an example of combined sublimable materials.

Percent Ingredient: by weight Strontium peroxide Calcium resinate 10 Bis (pdimethylaminophenyl)- methylenimine hydrochloride known as auramine dye 10 This formulation produces a yellow smoke trace visible by daylight to one thousand yards with no effect visible in the dark.

- v Percent Ingredient: I by weight Strontium peroxide 70 Calcium resinate 10 Anthracene 15 Powdered magnesium 5 This formulation operates to produce a black smoke trace visible to one thousand yards by daylight with a glow resolvable in the dark to one thousand yards.

I We claim:

1. A smoke tracer chlorate-free composition which will be readily ignitable within one-hundredth of a second by a propellant used to drive any standard projectile forward and which will withstand compression when placed inside of a projectile by a force greater than that developed by the thrust .of the propellant and which has been come pressed under about 110,000 p. s. i. during loading without undergoing ignition to a point where the composition has a density of 2 grms./cc., this high compression serving to prevent dislodgement of the composition when the projectile is fired, whereby 5 to 80 grains of this com position will cause a rearward trail of colored smoke which is sufficiently voluminous to be visible to a gunner firing said projectile over an entire range of at least 1,000 yards when the projectile is in flight from the muzzle of a gun to the target, the composition having the further property of rapid ignition without rapid burning, the combination therewith of a composition consisting of 50% to 80% of a peroxide of an alkaline earth metal selected from the group consisting of barium, strontium and calcium, 5% to 20% of calcium resinate, and 5% to 25% of at least one sublimable dye material selected from the group consisting of '1 methylamino-anthraquinone, 1,4-dimethylaminoanthraquinone, ortho dihydroxy benzene known in the trade as pyrocatechol; bis (p-dimethylaminophenyl)-methylenimine hydrochloride known in the trade as auramine dye.

2. A smoke tracer composition according to claim 1 which consists of 70% strontium peroxide, 15% calcium resinate and 15% of l-methylaminoanthraquinone.

3. A smoke tracer composition according to claim 1 which consists of 70% strontium peroxide, 10% calcium resinate, 10% l -methylaminoanthraquinone, 10% of ortho References Cited in the file of this patent UNITED STATES PATENTS Gowdy Oct. 7, 1919 Gowdy Oct. 21, 1919 6 Meek Apr. 9, 1929 Meek Apr. 9, 1929 Meek Apr. 29, 1930 Lucas Sept. 5, 1933 Hale Sept. 27, 1938 Ture May 10, 1949 Clarke et al. July 15, 1952 FOREIGN PATENTS Great Britain May 15, 1919 OTHER REFERENCES Eppig: J. Soc. D. and 0, December 1946, pp. 386, 387. Chemical and Engineering News, Colored Signal Smokes, pp. 1990, 1991 and 2056, November 25, 1944. 

1.
 1. A SMOKE TRACER CHLORATE-FREE COMPOSITION WHICH WILL BE READILY IGNITABLE WITHIN ONE-HUNDREDTH OF A SECOND BY A PROPELLANT USED TO DRIVE ANY STANDARD PROJECTILE FORWARD AND WHICH WILL WITHSTAND COMPRESSION WHEN PLACED INSIDE OF A PROJECTILE BY A FORCE GREATER THAN THAT DEVELOPED BY THE THRUST OF THE PROPALLANT AND WHICH HAS BEEN COMPRESSED UNDER ABOUT 110,000 P.S.I. DURING LOADING WITHOUT UNDERGOING IGNITION TO A POINT WHERE THE COMPOSITION HAS A DENSITY OF 2 GRMS./CC., THIS HIGH COMPRESSION SERVING TO PREVENT DISLODGEMENT OF THE COMPOSITION WHEN THE PROJECTILE IS FIRED, WHEREBY 5 TO 80 GRAINS OF THIS COMPOSITION WILL CAUSE A REARWARD TRAIL OF COLORED SMOKE WHICH IS SUFFICIENTLY VOLUMINOUS TO BE VISIBLE TO A GUNNER FIRING SAID PROJECTILE OVER AN ENTIRE RANGE OF AT LEAST 1,000 YARDS WHEN THE PROJECTILE IS IN FLIGHT FROM THE MUZZLE OF A GUN TO THE TARGET, THE COMPOSITION HAVING THE FURTHER PROPERTY OF RAPID IGNITION WITHOUT RAPID BURNING THE COMBINATION THEREWITH OF A COMPOSITION CONSISTING OF 50% TO 80% OF A PREROXIDE OF AN ALKALINE EARTH METAL SELECTED FROM THE GROUP CONSISTING OF BARIUM, STRONTIUM AND CALCIUM, 5% TO 20% OF CALCIUM RESINATE, AND 5% TO 25% OF AT LEAST ONE SUBLIMABLE DYE MATERIAL SELECTED FROM THE GROUP CONSISTING OF 1-METHYLAMINO-ANTHRAQUINONE, 1,4-DIMETHYLAMINOANTHRAQUINONE, ORTHO DIHYDROXY BENZENE KNOWN IN THE TRADE AS PYROCATECHOL; BIS (P-DIMETHYLAMINOPHENYL)-METHYLENIMINE HYDROCHLORIDE KNOWN IN THE TRADE AS AURAMINE DYE. 